to smile in a silly or unpleasant way that shows that you are pleased with yourself, know sth that other people do not know, etc. 自鸣得意地笑；傻笑
It was hard not to smirk.
让人忍俊不禁。
He smirked unpleasantly when we told him the bad news.
我们把坏消息告诉他时，他脸上现出一丝奸笑。